Normal cellular prion protein (PrP) is a highly conserved, widely expressed, glycophospholinositol (GPI)-anchored cell surface glycoprotein. Since its discovery, most studies on PrP have focused on its role in a group of neurodegenerative conditions, known as prion diseases. Little is known about PrP outside the nervous system.
The synthesis, processing and transit of PrP to the cell surface are complex and not completely understood. Normally, PrP is present in lipid rafts and can function as a signaling molecule.
PrP has many binding partners, such as glycosyaminoglycans, copper, laminin receptor, N-CAM, heat shock proteins, dystroglycan, stress-inducible protein, selectin and glypican-1. PrP also binds Grb2, an adapter protein, lipids and nucleic acids. PrP plays a role in apoptosis in a cell context dependent manner.
Prions prevent neuronal cell-line death. A recent study found that normal PrP is involved in the proliferation of epithelial cells and in the distribution of junction associated proteins in human enterocytes in vitro and in intestine in vivo. On the other hand, since the PrP deficient (Prnp−/−) mouse is viable and appears to be normal, the physiologic functions of PrP remain an enigma.